Technical Field
The present disclosure relates to a process for manufacturing a MEMS (Micro-ElectroMechanical Systems) pressure sensor and to a corresponding MEMS pressure sensor.
Description of the Related Art
Integrated semiconductor pressure sensors made using micromachining techniques, typical of MEMS, are known.
These sensors are, for example, used within portable or wearable electronic apparatuses, or in the automotive field, for example, for barometric applications.
In particular, piezoresistive pressure sensors are known, whose operation is based on piezoresistivity, i.e., on the capacity of some materials to modify their resistivity as the mechanical stresses to which they are subjected vary. For instance, the resistivity decreases when compressive stresses are applied, whereas it increases when tensile stresses are applied.
Piezoresistive pressure sensors generally include a membrane (or diaphragm), which is suspended over a cavity provided in a body of semiconductor material and undergoes deformation in the presence of incident pressure waves coming from the external environment.
Piezoresistive elements (generally constituted by implanted or diffused doped regions) are provided in a surface region of the membrane and are electrically connected to one another in Wheatstone-bridge configuration.
Deformation of the membrane causes an unbalancing of the Wheatstone bridge, which can be detected by a purposely provided electronic circuit (coupled to the micromechanical structure of the sensor), the so-called ASIC (Application-Specific Integrated Circuit), which derives, from said unbalancing, the value of pressure acting on the membrane.
Even though these piezoresistive pressure sensors are used widely and successfully, the present Applicant has realized that they have some disadvantages, at least for certain applications.
In particular, the present Applicant has realized that this type of sensors has in general a non-linear response as a function of temperature, i.e., a high thermal coefficient (TCO). The detection sensitivity moreover is dependent on the temperature and generally deteriorates as temperature increases.
Consequently, use of these sensors for applications that envisage high operating temperatures, or in general extensive temperature variations, may not be advisable.
The manufacturing process is moreover rather complex and costly, on account of the need for several implant or diffusion masks, for example to obtain the doped regions for formation of the piezoresistive elements within the membrane.
Furthermore, these piezoresistive pressure sensors do not allow convenient implementation of self-test procedures, for testing proper functionality thereof during operation.
In this regard, it is known that in some contexts of application, for example, in the automotive field, the self-testing capability is expressly desired to electronic systems in order to prevent errors and failure.